Evaluation of the fracture resistance and failure types of different CAD-CAM ceramic crowns supported by angled titanium abutments

Purpose To evaluate the fatigue resistance of computer-aided design and computer-aided manufacturing (CAD-CAM) single-ceramic crowns which were applied on angled implant abutments after thermomechanical aging. Materials and Methods Titanium abutments (N = 72, MODE Medical Dental Implant, Turkey) with three different angles (0, 15 degrees, and 25 degrees) were restored using different materials (monolithic zirconia [Zir], lithium silicate ceramic reinforced by zirconia [VS], and hybrid ceramic [VE]). Crowns in the maxillary first premolar form were cemented to abutments using resin cement (Panavia 2.0 Introkit). Dynamic loading and thermomechanical aging were applied to the specimens (120,000 cycles, 49 N, 5-55 degrees C). Fracture resistance values were measured in the universal test machine and fracture types were determined. Two-way ANOVA and Tukey test were used for statistical analysis (Jamovi version 2.3.5). Results Both the abutment angle and the type of material had a significant effect on fracture resistance (F = 3.295, p < 0.05). The highest fracture resistance was obtained in Group 0-Zir, and the lowest fracture resistance was obtained in Group 15-VE. Fracture resistance showed significant differences between Group 0 and Group 15 for the Zir and VE materials, and between Group 0 and Group 25 for VS (p < 0.05); no statistical significance was determined between the other groups (p>0.05). When failure types were evaluated, they were seen to be full or partial crown fractures, and abutment deformation was found in some samples. Conclusions Monolithic crowns may be preferred on angled abutments. The fracture resistance of CAD-CAM materials decreases as the angle of abutments increases. Monolithic zirconia has higher fracture resistance than other materials.